Such closure means for a cylindrical housing, in particular a blood sample tube, is disclosed in AT-A-379 069. This closure means comprises a cap surrounding an open end face of the cylindrical housing and defining a bore, a seal being provided in the bore and the interior of the housing. In the bore or in a tubular extension adjoining the bore, there are provided projections which protrude over the surface of the cap, the projections being covered by the seal. It cannot always be ensured, however, that the closure means can be opened without allowing the escape of medicaments or body fluids that may be contained in the cylindrical housing, in dependence upon the adhesion between the seal and the housing.
Also, closure means for cylindrical housings, in particular for medicaments or body fluids, are known, which comprise a one piece cap or a cap made up of several pieces, for use with a seal. For example, U.S. application Ser. No. 4 465 200, U.S. application Ser. No. 4 205 754, U.S. application Ser. No. 4 089 432, EP-B-129 029 and EP-A-257 498 concern the closure of an open end face of a cylindrical housing by means of a plug like seal secured in the housing by means of a cap. In such closure means very substantial force must be applied longitudinally of the cylindrical housing, in order to overcome the adhesion between the seal and the housing, so that the contents, for example, medicaments or body fluids stored in the housing, may escape and thus give rise to burns or infection. Such escape is especially disadvantageous in the processing of blood infected with AIDS. Also when the seal is pierced with a needle to remove a sample of the contents of the cylindrical housing, the closure means may be inadvertently opened.